Rybka Aquarium Opening book is based on five sources:
* Grandmaster evaluations (over 100,000 positions);
* Evaluations from the CAP Data (over 45 million positions);
* Evaluations from the Rybka CAP Data (20 million positions);
* Statistics from the DirectTree (opening positions from more than 3.5 million games);
* Powerful tools for user corrections and add-ons.